Make keyed operations use the unchecked index but still depend on the checked one.

src/hydrogen-instructions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 329 matching lines @@
   bool IsNone() const { return kind_ == kNone; }
   bool IsTagged() const { return kind_ == kTagged; }
   bool IsInteger32() const { return kind_ == kInteger32; }
   bool IsDouble() const { return kind_ == kDouble; }
   bool IsExternal() const { return kind_ == kExternal; }
   bool IsSpecialization() const {
     return kind_ == kInteger32 || kind_ == kDouble;
   }
   const char* Mnemonic() const;
 
+  Representation KeyedAccessIndexRequirement() {
+    // This is intended to be used in RequiredInputRepresentation for keyed
+    // loads and stores to avoid inserting unneeded HChange instructions:
+    // keyed loads and stores can work on both int32 and tagged indexes.
+    return IsInteger32() ? Integer32() : Tagged();
+  }
+
  private:
   explicit Representation(Kind k) : kind_(k) { }
 
   // Make sure kind fits in int8.
   STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));
 
   int8_t kind_;
 };
 
 
@@ skipping 2459 matching lines @@
 
   HValue* receiver() { return OperandAt(0); }
   HValue* function() { return OperandAt(1); }
 
   virtual HValue* Canonicalize();
 
   DECLARE_CONCRETE_INSTRUCTION(WrapReceiver)
 };
 
 
+enum BoundsCheckKeyMode {
+  DONT_ALLOW_SMI_KEY,
+  ALLOW_SMI_KEY
+};
+
+
+class HBoundsCheck: public HTemplateInstruction<2> {
+ public:
+  HBoundsCheck(HValue* index, HValue* length,
+               BoundsCheckKeyMode key_mode = DONT_ALLOW_SMI_KEY)
+      : key_mode_(key_mode) {
+    SetOperandAt(0, index);
+    SetOperandAt(1, length);
+    set_representation(Representation::Integer32());
+    SetFlag(kUseGVN);
+  }
+
+  virtual Representation RequiredInputRepresentation(int arg_index) {
+    if (key_mode_ == DONT_ALLOW_SMI_KEY ||
+        !length()->representation().IsTagged()) {
+      return Representation::Integer32();
+    }
+    // If the index is tagged and isn't constant, then allow the length
+    // to be tagged, since it is usually already tagged from loading it out of
+    // the length field of a JSArray. This allows for direct comparison without
+    // untagging.
+    if (index()->representation().IsTagged() && !index()->IsConstant()) {
+      return Representation::Tagged();
+    }
+    // Also allow the length to be tagged if the index is constant, because
+    // it can be tagged to allow direct comparison.
+    if (index()->IsConstant() &&
+        index()->representation().IsInteger32() &&
+        arg_index == 1) {
+      return Representation::Tagged();
+    }
+    return Representation::Integer32();
+  }
+  virtual Representation observed_input_representation(int index) {
+    return Representation::Integer32();
+  }
+
+  virtual void PrintDataTo(StringStream* stream);
+
+  HValue* index() { return OperandAt(0); }
+  HValue* length() { return OperandAt(1); }
+
+  DECLARE_CONCRETE_INSTRUCTION(BoundsCheck)
+
+  static HValue* ExtractUncheckedIndex(HValue* index) {
+    return index->IsBoundsCheck() ? HBoundsCheck::cast(index)->index() : index;
+  }
+
+ protected:
+  virtual bool DataEquals(HValue* other) { return true; }
+  BoundsCheckKeyMode key_mode_;
+};
+
+
 class HApplyArguments: public HTemplateInstruction<4> {
  public:
   HApplyArguments(HValue* function,
                   HValue* receiver,
                   HValue* length,
                   HValue* elements) {
     set_representation(Representation::Tagged());
     SetOperandAt(0, function);
     SetOperandAt(1, receiver);
     SetOperandAt(2, length);
@@ skipping 58 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(ArgumentsLength)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
  private:
   virtual bool IsDeletable() const { return true; }
 };
 
 
-class HAccessArgumentsAt: public HTemplateInstruction<3> {
+class HAccessArgumentsAt: public HTemplateInstruction<4> {
  public:
-  HAccessArgumentsAt(HValue* arguments, HValue* length, HValue* index) {
+  HAccessArgumentsAt(HValue* arguments,
+                     HValue* length,
+                     HValue* checked_index) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     SetOperandAt(0, arguments);
     SetOperandAt(1, length);
-    SetOperandAt(2, index);
+    SetOperandAt(2, HBoundsCheck::ExtractUncheckedIndex(checked_index));
+    SetOperandAt(3, checked_index);
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
   virtual Representation RequiredInputRepresentation(int index) {
-    // The arguments elements is considered tagged.
-    return index == 0
-        ? Representation::Tagged()
-        : Representation::Integer32();
+    switch (index) {
+      // The arguments elements is considered tagged.
+      case 0: return Representation::Tagged();
+      case 1: return Representation::Integer32();
+      case 2: return Representation::Integer32();
+      // The checked index is a control flow dependency to avoid hoisting
+      // and therefore it has no representation requirements.
+      case 3: return Representation::None();
+      default: { UNREACHABLE(); return Representation::None(); }
+    }
   }
 
   HValue* arguments() { return OperandAt(0); }
   HValue* length() { return OperandAt(1); }
   HValue* index() { return OperandAt(2); }
+  HValue* checked_index() { return OperandAt(3); }
 
   DECLARE_CONCRETE_INSTRUCTION(AccessArgumentsAt)
 
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
-enum BoundsCheckKeyMode {
-  DONT_ALLOW_SMI_KEY,
-  ALLOW_SMI_KEY
-};
-
-
-class HBoundsCheck: public HTemplateInstruction<2> {
- public:
-  HBoundsCheck(HValue* index, HValue* length,
-               BoundsCheckKeyMode key_mode = DONT_ALLOW_SMI_KEY)
-      : key_mode_(key_mode) {
-    SetOperandAt(0, index);
-    SetOperandAt(1, length);
-    set_representation(Representation::Integer32());
-    SetFlag(kUseGVN);
-  }
-
-  virtual Representation RequiredInputRepresentation(int arg_index) {
-    if (key_mode_ == DONT_ALLOW_SMI_KEY ||
-        !length()->representation().IsTagged()) {
-      return Representation::Integer32();
-    }
-    // If the index is tagged and isn't constant, then allow the length
-    // to be tagged, since it is usually already tagged from loading it out of
-    // the length field of a JSArray. This allows for direct comparison without
-    // untagging.
-    if (index()->representation().IsTagged() && !index()->IsConstant()) {
-      return Representation::Tagged();
-    }
-    // Also allow the length to be tagged if the index is constant, because
-    // it can be tagged to allow direct comparison.
-    if (index()->IsConstant() &&
-        index()->representation().IsInteger32() &&
-        arg_index == 1) {
-      return Representation::Tagged();
-    }
-    return Representation::Integer32();
-  }
-  virtual Representation observed_input_representation(int index) {
-    return Representation::Integer32();
-  }
-
-  virtual void PrintDataTo(StringStream* stream);
-
-  HValue* index() { return OperandAt(0); }
-  HValue* length() { return OperandAt(1); }
-
-  DECLARE_CONCRETE_INSTRUCTION(BoundsCheck)
-
- protected:
-  virtual bool DataEquals(HValue* other) { return true; }
-  BoundsCheckKeyMode key_mode_;
-};
-
-
 class HBitwiseBinaryOperation: public HBinaryOperation {
  public:
   HBitwiseBinaryOperation(HValue* context, HValue* left, HValue* right)
       : HBinaryOperation(context, left, right) {
     SetFlag(kFlexibleRepresentation);
     SetFlag(kTruncatingToInt32);
     SetAllSideEffects();
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
@@ skipping 1334 matching lines @@
   virtual HValue* GetKey() = 0;
   virtual void SetKey(HValue* key) = 0;
   virtual void SetIndexOffset(uint32_t index_offset) = 0;
   virtual bool IsDehoisted() = 0;
   virtual void SetDehoisted(bool is_dehoisted) = 0;
   virtual ~ArrayInstructionInterface() { };
 };
 
 
 class HLoadKeyed
-    : public HTemplateInstruction<3>, public ArrayInstructionInterface {
+    : public HTemplateInstruction<4>, public ArrayInstructionInterface {
  public:
   HLoadKeyed(HValue* obj,
-             HValue* key,
+             HValue* checked_key,
              HValue* dependency,
              ElementsKind elements_kind)
       : bit_field_(0) {
     bit_field_ = ElementsKindField::encode(elements_kind);
-
     SetOperandAt(0, obj);
-    SetOperandAt(1, key);
+    SetOperandAt(1, HBoundsCheck::ExtractUncheckedIndex(checked_key));
     SetOperandAt(2, dependency);
+    SetOperandAt(3, checked_key);
 
     if (!is_external()) {
       // I can detect the case between storing double (holey and fast) and
       // smi/object by looking at elements_kind_.
       ASSERT(IsFastSmiOrObjectElementsKind(elements_kind) ||
              IsFastDoubleElementsKind(elements_kind));
 
       if (IsFastSmiOrObjectElementsKind(elements_kind)) {
         if (IsFastSmiElementsKind(elements_kind) &&
             IsFastPackedElementsKind(elements_kind)) {
@@ skipping 21 matching lines @@
 
     SetFlag(kUseGVN);
   }
 
   bool is_external() const {
     return IsExternalArrayElementsKind(elements_kind());
   }
   HValue* elements() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
   HValue* dependency() { return OperandAt(2); }
+  HValue* checked_key() { return OperandAt(3); }
   uint32_t index_offset() { return IndexOffsetField::decode(bit_field_); }
   void SetIndexOffset(uint32_t index_offset) {
     bit_field_ = IndexOffsetField::update(bit_field_, index_offset);
   }
   HValue* GetKey() { return key(); }
   void SetKey(HValue* key) { SetOperandAt(1, key); }
   bool IsDehoisted() { return IsDehoistedField::decode(bit_field_); }
   void SetDehoisted(bool is_dehoisted) {
     bit_field_ = IsDehoistedField::update(bit_field_, is_dehoisted);
   }
   ElementsKind elements_kind() const {
     return ElementsKindField::decode(bit_field_);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     // kind_fast:       tagged[int32] (none)
     // kind_double:     tagged[int32] (none)
     // kind_external: external[int32] (none)
     if (index == 0) {
       return is_external() ? Representation::External()
           : Representation::Tagged();
     }
-    if (index == 1) return Representation::Integer32();
+    if (index == 1) {
+      return OperandAt(1)->representation().KeyedAccessIndexRequirement();
+    }
     return Representation::None();
   }
 
   virtual Representation observed_input_representation(int index) {
     return RequiredInputRepresentation(index);
   }
 
   virtual void PrintDataTo(StringStream* stream);
 
   bool RequiresHoleCheck() const;
@@ skipping 161 matching lines @@
 
   DECLARE_CONCRETE_INSTRUCTION(StoreNamedGeneric)
 
  private:
   Handle<String> name_;
   StrictModeFlag strict_mode_flag_;
 };
 
 
 class HStoreKeyed
-    : public HTemplateInstruction<3>, public ArrayInstructionInterface {
+    : public HTemplateInstruction<4>, public ArrayInstructionInterface {
  public:
-  HStoreKeyed(HValue* obj, HValue* key, HValue* val,
+  HStoreKeyed(HValue* obj, HValue* checked_key, HValue* val,
               ElementsKind elements_kind)
       : elements_kind_(elements_kind), index_offset_(0), is_dehoisted_(false) {
     SetOperandAt(0, obj);
-    SetOperandAt(1, key);
+    SetOperandAt(1, HBoundsCheck::ExtractUncheckedIndex(checked_key));
     SetOperandAt(2, val);
+    SetOperandAt(3, checked_key);
 
     if (is_external()) {
       SetGVNFlag(kChangesSpecializedArrayElements);
     } else if (IsFastDoubleElementsKind(elements_kind)) {
       SetGVNFlag(kChangesDoubleArrayElements);
       SetFlag(kDeoptimizeOnUndefined);
     } else {
       SetGVNFlag(kChangesArrayElements);
     }
 
     // EXTERNAL_{UNSIGNED_,}{BYTE,SHORT,INT}_ELEMENTS are truncating.
     if (elements_kind >= EXTERNAL_BYTE_ELEMENTS &&
         elements_kind <= EXTERNAL_UNSIGNED_INT_ELEMENTS) {
       SetFlag(kTruncatingToInt32);
     }
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     // kind_fast:       tagged[int32] = tagged
     // kind_double:     tagged[int32] = double
     // kind_external: external[int32] = (double | int32)
     if (index == 0) {
       return is_external() ? Representation::External()
                            : Representation::Tagged();
     } else if (index == 1) {
-      return Representation::Integer32();
+      return OperandAt(1)->representation().KeyedAccessIndexRequirement();
+    } else if (index == 3) {
+      return Representation::None();
     }
 
     ASSERT_EQ(index, 2);
     if (IsDoubleOrFloatElementsKind(elements_kind())) {
       return Representation::Double();
     }
 
     return is_external() ? Representation::Integer32()
                          : Representation::Tagged();
   }
@@ skipping 10 matching lines @@
     if (is_external()) {
       return Representation::Integer32();
     }
     // For fast object elements kinds, don't assume anything.
     return Representation::None();
   }
 
   HValue* elements() { return OperandAt(0); }
   HValue* key() { return OperandAt(1); }
   HValue* value() { return OperandAt(2); }
+  HValue* checked_key() { return OperandAt(3); }
   bool value_is_smi() const {
     return IsFastSmiElementsKind(elements_kind_);
   }
   ElementsKind elements_kind() const { return elements_kind_; }
   uint32_t index_offset() { return index_offset_; }
   void SetIndexOffset(uint32_t index_offset) { index_offset_ = index_offset; }
   HValue* GetKey() { return key(); }
   void SetKey(HValue* key) { SetOperandAt(1, key); }
   bool IsDehoisted() { return is_dehoisted_; }
   void SetDehoisted(bool is_dehoisted) { is_dehoisted_ = is_dehoisted; }
@@ skipping 122 matching lines @@
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
   // TODO(svenpanne) Might be safe, but leave it out until we know for sure.
   // private:
   //  virtual bool IsDeletable() const { return true; }
 };
 
 
-class HStringCharCodeAt: public HTemplateInstruction<3> {
+class HStringCharCodeAt: public HTemplateInstruction<4> {
  public:
-  HStringCharCodeAt(HValue* context, HValue* string, HValue* index) {
+  HStringCharCodeAt(HValue* context, HValue* string, HValue* checked_index) {
     SetOperandAt(0, context);
     SetOperandAt(1, string);
-    SetOperandAt(2, index);
+    SetOperandAt(2, HBoundsCheck::ExtractUncheckedIndex(checked_index));
+    SetOperandAt(3, checked_index);
     set_representation(Representation::Integer32());
     SetFlag(kUseGVN);
     SetGVNFlag(kDependsOnMaps);
     SetGVNFlag(kChangesNewSpacePromotion);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
-    // The index is supposed to be Integer32.
-    return index == 2
-        ? Representation::Integer32()
-        : Representation::Tagged();
+    switch (index) {
+      case 0: return Representation::Tagged();
+      case 1: return Representation::Tagged();
+      // The index is supposed to be Integer32.
+      case 2: return Representation::Integer32();
+      // The checked index is a control flow dependency to avoid hoisting
+      // and therefore it has no representation requirements.
+      case 3: return Representation::None();
+      default: { UNREACHABLE(); return Representation::None(); }
+    }
   }
 
   HValue* context() { return OperandAt(0); }
   HValue* string() { return OperandAt(1); }
   HValue* index() { return OperandAt(2); }
+  HValue* checked_index() { return OperandAt(3); }
 
   DECLARE_CONCRETE_INSTRUCTION(StringCharCodeAt)
 
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 
   virtual Range* InferRange(Zone* zone) {
     return new(zone) Range(0, String::kMaxUtf16CodeUnit);
   }
 
@@ skipping 550 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_